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Can't access addresses 0x00 - 0xFF of memory using XBYTE

I am using the XBYTE macro to access a memory mapped device. The chip select is being handled via another port (P1) to allow the full 64K of addresses to be axcessed. When I read data from the memory device I read 0x00 from addresses 0x00 - 0xFF. Above 0xFF the data reads correctly. I have verified that the memory device contains valid data in 0x00 - 0xFF address range. I also have scoped the RD line and it does appear that it is activated to read the data. Please let me know any thoughts. Thanks.

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